I used the opendir, readdir, and closedir native PHP functions, and it did the job quite well. The PHP class was named sfFinder, and it can still be found in all symfony versions. Even if the class is bundled with symfony, I know that a few people use it for all kind of stuff, not necessarily related to symfony. But the code starts to show its age; first because I learned a lot since then about PHP, and also because there is a better way now. Enter iterators!

He shows an example of how to use Iterators to search through directories recursively (RecursiveDirectoryIterator) and locate a certain filename. He also looks at making it more OOP and including filtering to remove files from the search. He's packaged up some of this logic into a new Symfony component - the Finder component - that can be used to locate files in a path, be restricted to a depth for the search, match regular expressions file names, filter by file size and much more.

If you'd like to dig into the code, check out this page on github for this new component (PHP 5.3 only).